Such tool-spindle arrangements are common in modern day machine tool construction. Such spindle arrangements are generally driven through a tooth system provided directly on the outside of the spindle or a gear arranged fixed against rotation on the spindle and a drive pinion cooperating therewith and connected through gears to a drive motor and, if necessary, connected after the drive motor. The drive motor--and, if necessary, the gear--are provided radially next to the tool spindle, so that generally a large and interfering size of construction results. To arrange the drive motor and a gear connected thereto as an axial extension of the spindle on its rearward end is generally not possible, since devices of the operating elements arranged inside of the hollow main spindle, for example tool vices, discharge-air pipes etc., are provided in this area.
A further disadvantage that exists with the known tool-spindle arrangements is that in every case, even if the drive motor is speed-controlled and a gear is not needed, a torque transmission through a tooth-system pairing takes place, which, as is known, results in the generation of noise and heat and requires a lubrication.
One purpose of the present invention is to provide a tool-spindle arrangement driven by an electric motor which requires little expense in its construction and in which a power transmission through gear pairings is avoided.
Another purpose of the invention is to provide a two-section tool spindle having a hollow spindle section connected at an axial end thereof to an axial end of a motor shaft section, wherein the motor shaft section includes a pressurized fluid carrying channel to facilitate supplying pressurized fluid to a tool receiving end of the spindle section.
The motor shaft of the electrical drive motor is itself constructed as a main spindle with all related operating components. The radial construction dimensions of the entire arrangement can in this manner be reduced to a minimum, namely the outer circumference of the drive motor itself. Any type of power transmission by a gear pairing is not needed and, thus, any type of noise and heat generation and the necessity for lubrication do not occur. The rear end part of the spindle remains free for the arrangement of the operating devices for operating the operating elements arranged inside of the drive spindle.
When the tool spindle is driven at one single speed, then an electric motor having a fixed operating speed is sufficient as a drive motor. However, in a preferred embodiment of the invention, the speed of the drive motor is adjustable with respect to its number of rotations per given time unit.
The main spindle is generally manufactured by the manufacturer of the machine tool, while the drive motor and thus also the motor shaft are supplier supplied parts. Therefore, one embodiment of the present invention provides that the main spindle includes of a front spindle section lying outside of the drive motor and a motor-shaft section coaxial thereto and lying substantially inside of the drive motor and which can be connected rotationally to the spindle section. Both sections are conformed structurally exactly to one another, for example with respect to their outside dimensions and the inside space. The spindle section is supported preferably in a separate spindle housing, the motor-shaft section in a motor housing. During the installation of the machine tool, the motor housing is secured on the spindle housing and at the same time the motor-shaft section, which is accessible at its two shaft ends, is coupled with the spindle section. Operating elements of the spindle arrangement, which operating elements are arranged inside of the spindle section, are at the same time coupled with corresponding operating elements arranged in the motor-shaft section, as will be discussed in greater detail in connection with on exemplary embodiment described below.
The drive motor is constructed in a preferred embodiment of the invention as a so called inner motor having an inner rotor arranged directly on the motor-shaft section and a stator arranged in the motor housing and enveloping the rotor.
Further developments of the invention result from the description of one exemplary embodiment. Such an exemplary embodiment is illustrated in the drawing and will be discussed in greater detail hereinbelow.